1. Field of the Invention
The present invention relates to a lens member and an optical unit using said lens member, used in, for example, LED lighting, and the like.
2. Related Art Statement
LED optical products such as lighting, projectors, flash, headlights and tail lamps of automobiles and the like, in which an LED is utilized as a light source, or basic optical devices such as a narrow directivity LED, and so on, generally use a lens for focusing or collimating the light emitted from the LED. Although a convex refractive lens is usually employed for this kind of lens, adoption of a Fresnel lens with the aim of height reduction and thinning is also proposed.
Conventionally, there is proposed a lens for a lamp fitting which has a lattice-shaped refracting system prism formed in a central portion of the inner surface near the optical axis, and also has a lattice-shaped reflecting system prism formed in a peripheral portion of this lattice-shaped refracting system prism (refer, for example, to JP 57-55002 A). In addition, there is proposed a Fresnel lens in which a part of the prisms of the Fresnel lens surface acting as a light-entrance surface is formed such that a part of the entering light rays are emitted from the light-exit surface after being totally internally reflected at the non-lens surface (refer, for example, to JP 59-119340 A). Furthermore, there is proposed an optical device configured from a refractive lens portion having a lens body provided at a central portion of the optical axis and a reflecting body portion, the reflecting body portion allowing light rays to enter from an inner surface portion and totally internally reflecting the light rays at a paraboloid-shaped reflecting surface, thereby converting the light rays into a parallel beam (refer, for example, to JP 05-281402 A).
However, the above-mentioned conventional technology leaves the following problems. That is, the lenses disclosed in JP 57-55002 A, JP 59-119340 A, and JP 05-281402 A have the disadvantage that a loss is generated due to a part of the entering light not reaching the reflecting surface, making it difficult to maximize usage efficiency of the light. For example, in JP 05-281402 A, there is a portion between the light-entrance surface and the refractive lens portion where the entering light does not reach the reflecting surface, resulting in loss of the light passing through this portion.
In addition, when an LED is used as the light source, the radiated light has a light distribution in which the greater the emission angle the smaller the light intensity; therefore, as shown in FIG. 29, when a conventional TIR (Total Internal Reflection) lens 1 is used, the light entering from the light-entrance surface of the concave lens portion 3 of the TIR lens 1 disposed to face the light source 2 is totally internally reflected at the reflecting surface of the outer convex lens portion 4; however, this results in the light L2 of relatively strong light intensity in the central portion vicinity being reflected at the reflecting surface at the outer peripheral area of the convex lens portion 4.
Consequently, in this TIR lens 1, brightness in the central vicinity is high, but becomes low in the intermediate vicinity and rises again at the outside. As a result, even if this TIR lens 1 is turned into a Fresnel lens, if a conventional method is used to do so, ring-shaped flare centered on the optical axis is generated which spoils the appearance.
Furthermore, in the lens disclosed in JP 05-281402 A, the light-entrance surface and light-exit surface of the reflecting lens portion are both formed as non-spherical surfaces, and there is therefore a problem that both processing is difficult and costs rise.
In addition, cases such as this lens, where a convex refractive lens portion is formed in the center, or where the central vicinity is a flat-shaped light-entrance surface, have the disadvantage that color variability of the light source can be seen on the light radiating surface.